Curves

Clive R. Haynes FRPS

 

On the previous page we looked at many examples, in table form, showing some of the limitless combinations of adjustment available to us, with this 'background information', we'll continue our exploration of 'Curves'.
 
It's possible to 'anchor' different points along the curve so that they remain fixed (either in place on the straight line or 'fixed' once the curve has been made). Let's take an example where the lower part of the curve remains fixed and the upper section is 'curved'.

Above: Let's examine what's happening in the dialogue box above.
The pale red line indicates the starting point for the curve - we can refer to this as the 'normal position'. Any distortion or movement from 'normal' will affect the image in some way. It's a good idea to always bear in mind the original slope of the line from corner to corner when making changes to the shape of the curve. The changes can be mentally related to the starting point.
As mentioned previously, some people place a pen on the monitor screen from corner to corner to see just how far from the straight line they have moved the 'Curve'.

By clicking on the line before we moved the upper section, two 'anchor points' were secured. You'll find when bending the curve that it's a bit like a seesaw, moving one part affects another so 'anchor points' keep unwanted distortions to a minimum.

In the example above, the upper-mid and lighter tones of the image have been lightened, whilst the lower mid-tones, dark greys and black have remained constant

By now you'll be able to appreciate some of the great control that can be exercised over an image.

 

What is an 'S Curve'
An 'S' curve is one that increases the contrast of the image and in many ways mimics the response curve of a photographic film. Sometimes it's useful to apply to an image, let's take a look.
Above: By clicking on the centre point this 'anchors' its position. The upper section and lower section of the curve was then adjusted to forma lazy 'S' and by so doing increases the contrast. The light tones have been forced nearer to peak white and the dark tones forces to nearer absolute black, whilst the mid greys remain closer to the starting point.
We'll continue explore some more on the next page - click on the link.

Next Page

Previous Page

Know-How Contents
Homepage
e-mail CRHfoto